U.S. Pat. No. 4,064,368 of the same assignee discloses a personal emergency response system for monitoring the needs of elderly or infirm persons confined to their residences. A typical system employs a subscriber unit located at a user site which, when activated, transmits an alert signal via a telephonic communication link to a central monitoring station. At the central monitoring station, directions are issued to dispatch aid to the residence from which the alert signal was received. Systems of this type have proven to be an effective tool for monitoring the condition and responding to the needs of elderly and/or infirm persons confined to their residences.
The system described above utilizes common telephone lines to communicate between a subscriber station and a central monitoring station. In the event of a natural disaster (e.g., floods, hurricanes, etc.), where telephone services may become disabled, the personal emergency response system will be rendered useless if it is unable to communicate with the central monitoring station. Thus, it is desirable to implement an alternative communications system into a personal emergency response system which allows the system user to receive or transmit information over a telephone-line independent, wireless channel, such as a radio frequency communication system.